19 replies to this topic

[croc7]

What is the desired result of drilling 4-6 1/8” diameter holes around the circumference of the thermostat? Doesn’t that defeat it’s purpose to regulate coolant temperature?

[nev100]

I think it allows the flow of water when the thermostat is closed as the pump is still spinning..

[nicklouse]

What is the desired result of drilling 4-6 1/8” diameter holes around the circumference of the thermostat? Doesn’t that defeat it’s purpose to regulate coolant temperature?

Nothing. All it does is increase the time it takes for the engine to get up to temp.

 

if you are using the correct one with the bleed valve in it with the wobbley thing in the rim there is no need to put any more holes is it as it will work as desired when it warms up.

[imack]

Engine never reaches operating temperature in cooler conditions with drilled stat.

[Steam]

It was a fix for engines minus the small bypass hose at the back of the head to block. To allow some flow before the tstat opens.

[sonscar]

So,Leyland made millions of Minis and did not do it?anecdotal evidence says do it?Which to believe eh?Just an older gents thoughts,Steve..

[mab01uk]

As said by Steam above i think this was mainly advised for Mini owners who fitted a Metro/late Mini engine/head that had the small by-pass hose connections blanked off and did not want to modify the head and water pump to fit one.

 

If the thermostat is completely removed for any reason then a thermostat blanking sleeve should be fitted as below.

 

"Removal of the thermostat helps to reduce engine temperature, however a thermostat blanking sleeve should be fitted to maintain correct coolant circulation to the entire head. Failure to do so will cause overheating around #3 and 4 combustion chambers, with obviously disastrous results. When the blanking sleeve is used it is also necessary to blank off the by-pass hose (not found on late heads) between the head and water pump."

https://www.minispar...sic/11G176.aspx

Edited by mab01uk, 14 September 2022 - 09:49 AM.

[Steve220]

Not sure on drilling loads of holes, but on the MPi, if it doesn't have a hole and a jiggle pin, then I always drill a 2mm hole to aid air bleeding as they're notoriously bad.

[Spider]

I've always blocked off the By-pass and never drilled the Thermostat. Let it do it's job.

[Northernpower]

It's an old fix for a problem that never existed. If you've fitted the correct stat with the bleed hole and pin in it you won't have a problem.

[andyapanel]

I have not seen a new thermostat with a bleed toggle in it for ages.

[PoolGuy]

I have not seen a new thermostat with a bleed toggle in it for ages.

 

https://www.minispar...sic/GTS106.aspx

[Lplus]

The joke is that the bleed hole and pin/ball shuts when the pump is in operation.  It only opens when the engines stops, presumably to let air pass up to the rad top.

 

The explanation given for the small holes was to ensure there is a flow of hot water past the thermostat enabling it to get hot and open as the water heats up.  It also ensures there is some flow within the head to prevent hotspots forming.  The open heater valve does allow flow in the head, but not ensure the thermostat gets a flow past it.  The MPi set up ensures water passes the thermostat by having the heater take off under the thermostat.

 

As to whether the engine reaches operating temp, well yes, for sure it does, at least mine does.

 

The original design with the bypass to shortcut the radiator ensured the thermosat had water flowing past it, then blocked the bypass with a shield when the thermostat opened.  That type or thermostat is long gone, though NOS can be found sometimes.

 

eg http://coventryautoc...&product_id=268

[mab01uk]

 

I have not seen a new thermostat with a bleed toggle in it for ages.

 

https://www.minispar...sic/GTS106.aspx

 

 

Quote from the Minispares link above:-

"It is possible to run thermostats with the troublesome bypass hose blanked off by drilling 4-6 holes 1/8" in size around the periphery of the thermostat."

 

[Lplus]

 

 

I have not seen a new thermostat with a bleed toggle in it for ages.

 

https://www.minispar...sic/GTS106.aspx

 

 

Quote from the Minispares link above:-

"It is possible to run thermostats with the troublesome bypass hose blanked off by drilling 4-6 holes 1/8" in size around the periphery of the thermostat."

 

I've use 3 X 3mm holes successfully.   On engines with the bypass I do wonder if a restrictor in the bypass might be beneficial, given the lack of shield on the thermostat to close the bypass off.